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Assessment Methods for Ammonia H o t-Sp o ts (Working Group 3)

Assessment Methods for Ammonia H o t-Sp o ts (Working Group 3). Expert Workshop under the UNECE Convention on Long-range Transboundary Air Pollution 4-6 Dec 2006, Edinburgh, Scotland. Outline. What is a hot-spot? How can they be assessed? Objectives Tools Modelling Uncertainties

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Assessment Methods for Ammonia H o t-Sp o ts (Working Group 3)

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  1. Assessment Methods for Ammonia Hot-Spots(Working Group 3) Expert Workshop under the UNECE Convention on Long-range Transboundary Air Pollution 4-6 Dec 2006, Edinburgh, Scotland

  2. Outline • What is a hot-spot? • How can they be assessed? • Objectives • Tools • Modelling • Uncertainties • Research Priorities • Integrated assessment • Models/Monitoring

  3. What is a hot-spot? • Large ammonia emission source • Localised either in space • Large ammonia emission source • Localised either in space or time

  4. How can they be assessed? • Objectives • Understanding small-scale processes • Assessing impacts of dry deposition • Spatial planning • Assessing effects of local abatement measures • Provide relationships for larger-scale models • Impact on air quality and PM formation • Modelling Tools • Lagrangian stochastic models • Local-scale Gaussian/Eulerian models • Screening/simple models (e.g. SCAIL)

  5. Uncertainties - Emissions • Suitable for source type • Temporally variable • Diurnal variation • Seasonal variation • In the correct location • Depends on objectives/accuracy Process-based ?

  6. Uncertainties – Exchange processes • Better knowledge of compensation point of natural vegetation and crops • Better knowledge/improvement of surface resistance = f(NH3, surface humidity) for different vegetation • Effect of deposition on compensation point and surface resistance • Need for in-canopy transfer/deposition + 2-layer model for simpler application

  7. Uncertainties – Specific to model type • Lagrangian Stochastic, short-range models: • Compensation point (Cp) • Effect of exposure to NH3 on Rw and Cp • Detailed turbulence field near buildings/forest edges • Gaussian/Eulerian models: • Compensation point (Cp) • Effect of exposure to NH3 on Rw and Cp • Chemistry (depending on spatial scale) • Accurate locations of sources and receptors • Screening/simple model: • Source strength, • Applicability to other locations/sources/receptors

  8. Spatial Planning Receptor buffer zones

  9. Linking to larger-scale modelling • Regional scale (e.g. EMEP) • Upscaling local interactions • Estimates of within-grid recapture • Providing boundary conditions • Use of local relationships at regional scale

  10. Use of local relationships at regional scale

  11. Assessment Strategies • Objectives • Modelling tools • Monitoring tools • Integrated approaches (model + monitoring)

  12. Assessment Strategies - Objectives • Existing or planned source • Single source and receptor • Multiple source-receptor (local measures) • Comparison with thresholds • Critical levels • Critical loads

  13. Assessment Strategies - Tools • Modelling tools • Simple/Landscape/Lagrangian Stochastic • Monitoring tools • Low cost e.g. passive samplers • Comparison with continuous measurement • Sampling period • Sampling locations • Biomonitoring ? • Methods for deposition measurement

  14. Assessment Strategies – Integrated approach? • Objectives (e.g. existing/planned source) • Combined modelling and monitoring? • Comparison with critical levels: • Measurements used to verify model predictions • Comparison with critical loads: • Concentration measurement  Deposition estimate • Deposition velocity approach probably too simplistic • Inferential modelling approach is better (and possible)

  15. Working Group Achievements • Assessed range of objectives • Prioritised uncertainties (for different model types) •  Research priorities • Concluded that model inter-comparisons would be very useful • Suggested possible assessment strategies • Depending on objectives (existing/planned source, single/multi-sources and receptors, comparisons with critical levels/loads)

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